I stand by my theory the mutation of Krang's clones is just a very, very, very ancient ancestor of the Utroms that ended up reverse engineering genetically.

I can't really think of a good comparison, but I'm aiming for one of the "weirder" transitions in evolution. Basically the only thing "modern" Utroms would have in common with their giant ancestors would be their spines, facial plates, and maybe shoulder joints, but the limbs would have either disappeared or multiplied over the eons.